This section is from the book "A Practitioner's Handbook Of Materia Medica And Therapeutics", by Thos. S. Blair. Also available from Amazon: A Practitioner's handbook of Materia Medica and Therapeutics.
Tolu. A mild expectorant, stimulant to the bronchial mucous membranes. It is seldom used alone, but the syrup carries nicely and promotes the action of more positive expectorants. The dispensing physician will find the "soluble fluid tolu" useful in compounding the syrup or extemporaneous mixtures.